1. Field of the Invention
This invention relates to a breathing apparatus which is used in water and on land, and particularly to a semi-closed type of breathing apparatus in which carbon dioxide is removed from breathing air circulating in a breathing circuit to use the breathing air, and the breathing air is supplemented into the breathing circuit from a air tank.
2. Description of Related Art
In general, the semi-closed type of breathing apparatus is equipped with a mouthpiece, a carbon dioxide absorber (canister) for absorbing carbon dioxide, a breathing bag and a pressure air tank. In the semi-closed type of breathing apparatus thus constructed, carbon dioxide is removed from the breathing air in the breathing circuit by the canister, and fresh air is supplied from the air tank into the breathing circuit while surplus breathing air is discharged from the breathing circuit.
A conventional semi-closed type of breathing apparatus is disclosed in Japanese Laid-open Patent Application No. 50-38397. The mouthpiece of the breathing apparatus as disclosed in this publication has two ducts connected to each other, that is, an air inhaling duct and an air exhaling duct which serve to circulate the air through the canister and are disposed separately from each other.
However, when the semi-closed type of breathing apparatus having the mouthpiece thus constructed is used, the two ducts of the air inhaling and exhaling ducts are arranged to extend from the face of an user to the right and left sides thereof, so that the user cannot smoothly carry the breathing apparatus on his back and detach it from his back. In addition, this construction mars the overall appearance of the breathing apparatus.
In view of the foregoing, one possible solution would be to bundle the two ducts. However, simply bundling of the ducts still mars the overall appearance of the breathing apparatus and does not meet the requirement of simplifying the entire construction of the apparatus.